08 mercury 90 efi, on Fisher freedom pontoon electrical problem

by Keith
(Greers ferry lake)

While docking at nite , I turn my docking lites on , and all of my lites and stock stereo go off .this happened last week. I went down to try and trouble shoot , I put key to aux ..tried to turn on stereo..and it worked ( I didn't play any sound), as well as the lites ...so I go out that nite ..come back to dock ...it happens again ...I am thinking the docking lites and stereo are the problem when both in use ...I checked fuses...they are not burned out ???